The present invention concerns a tube-like device for transferring ions generated by means of an ion generation source, comprising a cylindrical middle portion and an inlet portion to introduce ions in at least one ion cloud into the cylindrical middle portion, wherein at least one flow direction of the ions is along a longitudinal axis of the tube-like device.
In analytical chemistry, to determine the composition of unknown analytes, frequently mass spectrometry is used. The specimen composition to be tested is transformed by an ion generation source at atmospheric pressure from liquid or solid state to gaseous phase and ionised or fragmented, respectively. The resulting ions undergo acceleration in an electrical field, are transferred to a vacuum atmosphere through a known capillary and further analyzed by mass-spectroscopy according to the mass-to-charge ratio (m/z ratio).
The capillary has an orifice arranged centrally in the longitudinal direction through which the gaseous phase containing ions or ion fragments flows in the direction of the analyser. In the known manner such orifices in the longitudinal direction of the capillary have a constant diameter of less than 1 mm.
The embodiments known from the prior art are disadvantageous because the gaseous ion cloud emerging from the ion generation source expands due to space charge effects. Thus, only a small percentage of around 1-10% of generated ions are transferred through the central channel of the capillary towards the analyser [1]. The remaining 90-99% of the generated ions hit the outer surface of the capillary and are therefore not analysed, detected or transmitted.
Furthermore the geometric form of the capillaries known from the prior art causes perturbations in the gas flow at the capillary entrance, especially at the edges like for example stall or vortex flow, inducing further ion losses and reducing the ion yield at the analyser.
Due to the low yield long time periods are needed in order to achieve sufficient material quantities for further analysis.
The object of the present invention is therefore to provide a tube-like device for transferring an increased amount of ions generated by an ion generation source and to reduce ion losses. Moreover, the object of the present invention is to realize a detection of almost all contents of a desired sample. Moreover, the object of the present invention is to provide fast screening measurements.
This object is achieved by the device according the features of claim 1. Advantageous embodiments and refinements are the subject of the subclaims.